1. Field of the Invention
This invention relates to intravascular expandable devices and delivery systems for implantation within a vessel of the body, and more particularly to an expandable stent and delivery system which may be used in the treatment of blood vessel disorders. More specifically, the expandable stent and delivery system may be used in the treatment of blood vessel blockage and aneurysms which occur in the brain.
2. Description of the Prior Art
On a worldwide basis, nearly one million balloon angioplasties were performed in 1997 to treat vascular disease, including blood vessels clogged or narrowed by a lesion or stenosis. The objective of this procedure is to increase the inner diameter or cross-sectional area of the vessel passage, or lumen, through which blood flows.
In an effort to prevent restenosis without requiring surgery, short flexible cylinders or scaffolds, made of metal or polymers, are often placed into a vessel to maintain or improve blood flow. Referred to as stents, various types of these devices are widely used for reinforcing diseased blood vessels, for opening occluded blood vessels, and for defining an internal lumen to relieve pressure in an aneurysm. Stents allow blood to flow through the vessels at an improved rate while providing the desired lumen opening or structural integrity lost by the damaged vessels. Some stents are expanded to their proper size by inflating a balloon catheter, referred to as “balloon expandable” stents, while others are designed to elastically resist compression in a “self-expanding” manner.
Balloon expandable stents and self-expanding stents are generally delivered in a cylindrical form, compressed to a smaller diameter and are placed within a vessel using a catheter-based delivery system. When positioned at a desired site within a vessel, these devices are expanded by a balloon, or allowed to “self-expand,” to the desired diameter.
U.S. Pat. No. 4,768,507 entitled, “Intravascular Stent and Percutaneous Insertion Catheter System for the Dilation of an Arterial Stenosis and the Prevention of Arterial Restenosis” discloses a system used for placing a coil spring stent into a vessel for the purposes of enhancing luminal dilation, preventing arterial restenosis and preventing vessel blockage resulting from intimal dissection following balloon and other methods of angioplasty. The coil spring stent is placed into spiral grooves on an insertion catheter. A back groove of the insertion catheter contains the most proximal coil of the coil spring stent which is prevented from springing radially outward by a flange. The coil spring stent is deployed when an outer cylinder is moved proximally allowing the stent to expand.
Also, U.S. Pat. No. 6,126,684 entitled, “Apparatus and Methods for Placement and Repositioning of Intraluminal Prostheses” discloses a delivery catheter for a radially compressible tubular prosthesis including an elongated shaft slideably received within an elongated sheath. The prosthesis is carried over the distal end of the shaft where it is contained in a radially compressed configuration by the sheath. Penetrating stay members on the exterior of the shaft engage the proximal section of the prosthesis allowing the prosthesis to be recaptured prior to full release of the prosthesis.
Another stent and delivery system is disclosed in U.S. Pat. No. 6,214,036 entitled, “Stent Which is Easily Recaptured and Repositioned Within the Body.” This patent discloses a self-expanding stent which may be used in the treatment of aortic aneurysms. This device includes longitudinal legs having a flange which attaches to a delivery apparatus. The stent may be easily recaptured after placement and repositioned to a new position within the vessel. This patent, assigned to a related company, is subsequently referred to and the disclosure therein is incorporated and made a part of the subject patent application.
U.S. Pat. No. 6,361,558 entitled, “Stent Aneurysm Treatment System and Method” and assigned to the same assignee as the present application discloses other stent devices. This patent discloses vasculature stents of various configurations which may be used as aneurysm covers for occluding, or partially occluding, aneurysms located at various positions along the blood vessels.